In the manufacturing process of semiconductor devices, an important step is smoothing a surface of a device after it has been made. For example, the formation of various features or layers in a device may cause uneven topography, and this uneven topography may interfere with subsequent manufacturing processes, such as the photolithographic process. It is desirable to planarize the surface of the device, using known methods such as chemical mechanical polish (CMP), after various features or layers have been formed.
During a CMP process, a wafer is placed on a carrier. The carrier and the wafer are then rotated as downward pressure is applied to the wafer against a polishing pad. A chemical solution, referred to as a chemical slurry, is deposited onto the surface of the polishing pad and under the wafer to aid in the planarizing. Thus, the surface of the wafer may be planarized using a combination of mechanical (the grinding) and chemical (the slurry) forces.
After the CMP process has been applied to a wafer, some residues such as carbon or adhesive films and particles may stay on the top surface of the wafer. These films and particles may cause surface roughness leading to defects in subsequent fabrication processes, such as a defect in the photolithography process due to the uneven surface of the wafer.
In order to remove the residues from the wafer, post-CMP cleaning processes may be applied to the wafer. The post-CMP cleaning processes may include a brush cleaning process, a pencil cleaning process and a drying process. During the brush cleaning operation, a brush is brought into contact with the top surface of the wafer. During a relative movement between the brush and the wafer, the contaminants are removed from the wafer surface.
The pencil cleaning process is applied to the wafer after the brush cleaning process. During the pencil cleaning process, a pencil pad is brought into contact with the surface of the wafer. During a relative movement between the pencil pad and the wafer, the remaining contaminants are removed from the wafer surface.
During the brush and pencil cleaning processes, various cleaning liquids may be applied to the wafer and remain on the top surface of the wafer. The remaining liquids may be removed by a spin drying process.